This invention relates to the use of wheel rotation information and its correlation with accelerometer data to determine an out of balance wheel condition.
Modern vehicles are being provided with more and more electrical components to provide various functions. As an example, many modern vehicles are provided with ABS brake systems. An ABS brake system monitors a number of aspects of the rotation of the wheels. As one main aspect, an ABS system incorporates a wheel rotation sensor that senses up to 60 pulses per revolution of the wheel. This information is utilized to determine how and when brakes should be applied. This information has not been utilized for other diagnostic functions, however, but is easily available to a vehicle controller.
One main problem with tire wear on modern vehicles is an out of balance condition. Wheels have typically been balanced relative to each other during maintenance, and at a garage. The determination of when wheels are out of balance has typically been left to the maintenance function. There has not been an easy way of actively detecting an out of balance condition on the moving wheels. This results in undesirable tire wear.
The present invention discloses a method and apparatus for utilizing available information to determine an out of balance condition.
The present invention incorporates an accelerometer onto an axle of a vehicle. The accelerometer information determined by the sensor provides an indication of when there are acceleration peaks on the axle. Further, a sensor which determines wheel rotation is also fed to the controller. This sensor may be the sensor which is already provided as part of an ABS system. Such systems provide up to 60 pulses per tire revolution. The controller associates the rotation information with the accelerometer information temporally. That is, the acceleration information at each of the wheel rotational signals from the wheel sensor are associated.
If a wheel is out of balance, then a pattern of similar accelerations should be seen on each revolution of the wheel. The sensor can then look for peaks in the acceleration information, and see if those peaks are associated with a similar point of wheel rotation. If so, a signal can then be sent that the wheels are out of balance and should be checked. The present invention thus provides a simple, inexpensive and active way of determining an out of balance condition without the necessity of returning the vehicle to a garage for maintenance.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.